Each dairy producer globally is faced with challenges of transitioning each female that enters the milking string from pregnant to calving and ultimately efficiently produce enough milk to generate profit. In a year, farmers can lose up to 10% of their herds in the two months following calving due to health issues. Indeed, 75% of disease in dairy cows occurs in the first 60 days after a lactation begins with as much as 50% of high producing cows affected. Compounding the significance of ensuring healthy transition for cows is the economic commitment to treating transition period diseases. The cost per disease case per lactation is between $200 to $400 for each disease incidence. The total annual economic loss due to Metritis alone, in a dairy herd with 1,000 cows and an average disease incidence of 15% could reach up to $53,000, representing a significant economic burden.
The transition period is critical as the first and over-riding priority of a pregnant cow's body is to make milk, even at the expense of her own health. She will use her own energy reserves resulting in a negative energy balance which can have a negative impact on her short and long-term health. This is exacerbated by the cow's immune system suppression resulting from the pregnancy. Because of this behavior, and contrary to traditional logic, low milk production is not necessarily an indicator a cow has developed or is susceptible to a health issue during this period since a cow that does not transition well often is still a good milk producer.
Farmers have done their best to prevent and react to health issues that arise during the transition cow period with the tools available. As new management, animal health, and nutrition tools have been introduced, farmers have invested in them eagerly in hopes of minimizing the negative impact of health issues related to this transition period in each cow's life. Unfortunately the gains are generally temporary and the farmer must re-invest in the tools each time a cow goes through this period. Thus, there remains a need in the art for breeders to effectively minimize the need for additional preventative and reactionary measures while reducing the negative health issues a cow is susceptible to during the transition period. According to the invention, breeders can now change their approach and start selecting genetics for their herds demonstrated to effectively minimize the need for additional preventive and reactionary measures to transition cow health issues such as mastitis, metritis, and ketosis. Genetic selection is a cumulative and cost effective way to make permanent change to the herd so as to not have to rely on the cycle of prevention and treatment currently utilized.
Traditional breeding techniques involve the studying of sire progenies, and evaluating their milk production ratings (breeding values, or genetic merit) to guide further breeding. This standard technique requires years to evaluate the true genetic value by progeny testing each bull. Many cows must be bred and give birth to offspring. The females must be raised, bred, allowed to give birth and finally milked for a length of time to measure their phenotypic traits.
Furthermore, selection based purely on phenotypic characteristics does not efficiently take into account genetic variability caused by complex gene action and interactions, and the effect of the environmental and developmental variants. There is thus a need for a method of genetically evaluating cattle to enable breeders to more accurately select animals which display desirable phenotypic and the genetic traits.
Genomic selection can lower the high cost of progeny testing currently used to improve sires, since young bull progeny could be evaluated immediately after birth, and young bulls that are determined by genetic testing to have undesirable markers would never be progeny tested or even prior to birth, for the presence/absence of the marker. Traditional thinking is that genome wide markers are the best predictor of overall health and status of animals. Multiple loci located on separate regions of the genome such as different chromosomes can include at least 100, or at least 500, or at least 1000, or at least 5000 or more different loci.
It is an object of the present invention to identify critical traits from the thousands of traits, variation, and genetic markers available for selection and breeding that are highly correlated with successful transition to milk production.
Other objects will become apparent from the description of the invention which follows.